1. Field of the Invention
This invention relates to a motion adaptive type signal separator with a data companding function and, more particularly, to a digital video signal Y/C separator for Y/C-separating a composite video signal formed by frequency-multiplexing a plurality of signals, e.g., a composite TV signal of the frequency-multiplexed luminance signal (Y) and chrominance signals (C), by utilizing digital signal processing.
2. Description of the Related Art
Existing color TV broadcasting systems use a composite TV signal which is obtained by multiplexing the color subcarrier modulated by a chrominance difference signal with the luminance signal. For this reason, a receiver must perform luminance/chrominance separation (to be referred to as Y/C separation hereinafter). However, if signal separation is performed in a simple manner, this may result in image quality degradation such as cross-color or dot crawl, resulting from incomplete signal separation. Recently, a comb filter having excellent separation characteristics has been introduced for the purpose of improved Y/C separation. However, even when such a comb filter is used, there is no noticeable improvement in image resolution image in a helical direction.
With the aim of eliminating the above drawbacks, a so-called motion adaptive type Y/C separator has recently been developed for use in a digital TV system in which signal processing is performed digitally upon detection of a video signal, in order to obtain an image of particularly high quality. The motion adaptive type signal separator changes the parameters of its filter characteristics by detecting the motion data of a picture. This separator, which is described in SMPTE Journal, 1984, May, pp. 470-476, performs Y/C separation with respect to both a still picture and a motion picture, on the basis of operations between frames, using a frame memory, and on the basis of operations between lines, respectively.
However, such a motion-adaptive type signal separator requires a frame memory having a large capacity in order to perform Y/C separation with respect to a still picture. This requirement inevitably results in an increase in the size of the circuit, which poses problems in terms of unit cost.